Laid-open patent specification DE 198 53 669 A1 discloses an ultrashort-pulse source with controllable multiple-wavelength output, which is used especially in a multiphoton microscope. The system has an ultrashort-pulse laser for producing ultrashort optical pulses of a fixed wavelength and at least one wavelength conversion channel.
U.S. Pat. No. 6,097,870 discloses an arrangement for generating a broadband spectrum in the visible and infrared spectral range. The arrangement is based on a microstructured fibre, into which the light from a pump laser is injected. The pump light is broadened in the microstructured fibre by non-linear effects. So-called photonic band gap material or “photonic crystal fibres”, “holey fibres” or “microstructured fibres” are also employed as microstructured fibres. Configurations as a so-called “hollow fibre” are also known.
Another arrangement for generating a broadband spectrum is disclosed in the publication by Birks et al.: “Supercontinuum generation in tapered fibres”, Opt. Lett. Vol. 25, p.1415 (2000). A conventional optical fibre having a fibre core, which has a taper at least along a subsection, is used in the arrangement. Optical fibres of this type are known as so-called “tapered fibres”.
An optical amplifier, whose gain can be adjusted as a function of the wavelength, is known from the PCT application with the publication number WO 00/04613. The said publication also discloses a fibre light source based on this principle.
Arc lamps are known as broadband light sources, and are employed in many areas. One example is the U.S. Pat. 3,720,822 “XENON PHOTOGRAPHY LIGHT”, which discloses a xenon arc lamp for illumination in photography.
Especially in microscopy, endoscopy, flow cytometry, chromatography and lithography, universal illuminating devices with high luminance are important for the illumination of objects. In scanning microscopy, a sample is scanned with a light beam. To that end, lasers are often used as the light source. For example, an arrangement having a single laser which emits several laser lines is known from EP 0 495 930: “Konfokales Mikroskopsystem für Mehrfarbenfluoreszenz” [confocal microscope system for multicolour fluorescence]. Mixed gas lasers, especially ArKr lasers, are mainly used for this at present. Examples of samples which are studied include biological tissue or sections prepared with fluorescent dyes. In the field of material study, illumination light reflected from the sample is often detected. Solid-state lasers and dye lasers, as well as fibre lasers and optical parametric oscillators (OPOs), upstream of which a pump laser is arranged, are also frequently used.
Microspot arrays or so-called microplates are used in genetic, medical and biodiagnosis for studying large numbers of specifically labelled spots, which are preferably applied in a grid. A microplate reader which can be adjusted both in excitation wavelength and in detection wavelength is disclosed in the European Patient Application EP 0 841 557 A2.
The illumination methods and illuminating instruments known from the prior art have several disadvantages. The known broadband illuminating instruments mostly have a low luminance compared with laser-based illuminating devices, whereas the latter provide the user only with discrete wavelength lines whose spectral position and width can be adjusted only to a small extent, if at all. Owing to this limitation of the working spectrum, the known illuminating devices are not flexibly usable. Laser-based illuminating devices and illuminating methods also have the disadvantage that, owing to the high coherence of the laser light, disruptive interference phenomena, such as e.g. diffraction rings and Newton's rings, occur. To reduce these interference effects, additional optical elements are often used, which reduce the light power by intrinsic absorption and by scattering.